1. Field of the Invention
The present invention relates to intravenous infusion systems for introducing fluids into the human body, and more specifically, to level sensing and monitoring systems for detecting low levels of such fluids in containers supplying the fluids.
2. Description of the Related Art
The use of intravenous (IV) supply bags and bottles to introduce nutrient, therapeutic and medicinal fluids into the human body is well-known in the art. Typically, such systems have a container suspended above a patient by means of an IV bag stand or the like. The container is hung from the stand, and fluid flows from an IV spike inserted in the lower portion of the container through a delivery tube to an IV needle inserted into the patient, where it is infused into the patient's body.
To ensure a regular and uninterrupted flow of fluid to the patient, it is necessary to monitor the fluid level in the container so that it can be replaced when the fluid is low. Alternatively, the fluid in the container may be replenished. In either case, it is necessary to have an attendant continuously or periodically monitor the fluid level or provide an automated monitoring system. Common automated monitoring systems in use today are optoelectronic devices which monitor a clear portion of the delivery tube. When the fluid level falls below the IV spike fluid inlet port, air from the upper evacuated portion of the container enters the delivery tube. Upon detecting the bubbles in the delivery tube, the system activates an audible or visual alarm. It also may optionally terminate the fluid flow to avoid introducing the bubbles into the patient.
In an alternative system, the capacity of the container and a desired flow rate are used to calculate the period of time during which the flow can be maintained. The flow is initiated and controlled by an undulating track arrangement holding the IV line, and when the calculated time period elapses, the system activates an alarm.
While such systems are effective, they are not without disadvantages. For example, the systems are relatively complicated and consequently failure-prone. Moreover, they are expensive--in late 1993, an optoelectronic-type unit cost approximately $2000.